Confused(HUGE misunderstanding) about potentiometer (HS physics)

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    Physics Potentiometer
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Discussion Overview

The discussion revolves around the workings of a potentiometer, particularly addressing confusion regarding a specific circuit diagram and the absence of current in a branch loop. Participants explore the theoretical underpinnings of potentiometers, their practical applications, and the implications of voltage laws in circuit analysis.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about a diagram related to a potentiometer, questioning why there is no current in a branch loop despite applying voltage laws.
  • Another participant asserts that the provided diagram does not represent a potentiometer, explaining that a potentiometer functions as a variable voltage divider with a constant sum of resistances.
  • A third participant shares a link to a tutorial on potentiometers, suggesting it contains useful information for understanding the concept.
  • The original poster seeks clarification on the absence of current, reiterating their understanding of voltage laws and questioning the validity of their school's diagram.
  • Another participant emphasizes that a proper potentiometer circuit diagram should include a pair of resistors or a pot symbol, implying that the original diagram may be misleading.
  • A light-hearted comment is made about the representation of a wire in the diagram, suggesting a visual adjustment.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the validity of the diagram in question. There are competing views regarding the correct representation of a potentiometer and the implications of the absence of current in the discussed circuit.

Contextual Notes

The discussion highlights potential misunderstandings related to circuit diagrams and the application of voltage laws, but does not resolve these issues. The original diagram's accuracy and relevance to potentiometers remains uncertain.

qazxsw11111
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Hi everyone. I am extremely confused about how a potentiometer works.

In my notes, this is the diagram.

http://img25.imageshack.us/img25/5836/batteryu.jpg

In the branch loop, there is no current. I know this is correct, but I am confused by it. Assuming the current flows clockwise (arbitrary) in the branched circuit,
V(Of branch battery)=Pd across the length the wires are attached to. (By voltage law)

Shouldnt there be a current or something? Why is there no current? I know it is a terrible misunderstanding...

And also what practical use does a potentiometer in this case have? Is it just to see what pd a wire has?

Thanks a lot for your answers
 
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No wonder you are confused. That diagram has nothing to do with a potentiometer, as far as I can see. A pot is a variable voltage divider. The sum of the two divider resistances is constant, and the center tap position determines the divider ratio.

I'll dig up a good reference for you here in a sec...
 
Whew. Took a bit of searching, but finally found this link:

http://www.bourns.com/pdfs/trmrpmr.pdf

It's an excellent tutorial on potentiometers by Bourns, one of the larger manufacturer of pots. It's a classic, and filled with great and useful info.

BTW, the PF thread that I found the link in is also very useful. Check it out when you have tiime to read a long (but helpful) thread:

https://www.physicsforums.com/showthread.php?t=178516

.
 
Last edited by a moderator:
Whoa, that's a huge amount of info right there. Thanks. But what I don't understand is that you said it is not a potentiometer. Why? Thats the diagram my school printed in the notes. It is just that I don't understand why is there no current.
Because of voltage law and assuming current flows anticlockwise,
Total EMF=Total PD
EMF=I (R [A-B])
Shouldnt there be a current?
 
qazxsw11111 said:
Whoa, that's a huge amount of info right there. Thanks. But what I don't understand is that you said it is not a potentiometer. Why? Thats the diagram my school printed in the notes. It is just that I don't understand why is there no current.
Because of voltage law and assuming current flows anticlockwise,
Total EMF=Total PD
EMF=I (R [A-B])
Shouldnt there be a current?

A potentiometer circuit diagram will show a coupled pair of resistors ( or just a pot symbol ). The voltage sources are different and ancillary to the application.

Compare and contrast the circuit diagram you posted versus the diagrams in the very reputable App Note from Bourns. Which do you think is correct?
 
Perhaps red wire should be drawn as /\/\/\/\/\/\/\/\ :smile:
 

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